Process for the preparation of alpha nitrato-and alpha hydroxyisobutyric acids



- tions of oxidation and hydrolysis.

PRDCESS FOR THE PREPARATION OF ALPHA QIC'II'ISiQTO- AND ALPHAHYDROXYISOBUTYRIC James H. Gardner, Wayland, and Thomas R. Steadman,

Waban, Mass, assignors to Escambia Chemical Corporatlon, Pace, Fla., acorporation of Delaware No Drawing. Application January 6, 1958 SerialNo. 707,079 Claims. (Cl. 260466) This invention relates to theproduction of valuable chemicals and in particular to the production ofalpha hydroxyisobutyric acid and derivatives thereof. This applicationis, in part, a continuation of our copending application Serial No.637,858, filed February 4, 1957, and now abandoned.

A principal object of the present invention is to provide an economical,integrated process for making alpha nitratoisobutyric acid, alphahydroxyisobutyric acid and derivatives thereof from isobutylene.

Another object of the invention is to provide an economical integratedprocess for making methacrylic acid and esters thereof from isobutylene.

Still another object of the invention is to provide a process forconverting isobutylene to esters of alpha hydroxyisobutyric acid.

Other objects of the invention will in part be obvious and will in partappear hereinafter.

The invention accordingly comprises the process involving the severalsteps and the relation and order of one or more of such steps withrespect to each of the others which are exemplified in the followingdetailed disclosure, and the scope of the application of which will beindicated in the claims.

For a fuller understanding of the nature and objects of the invention,reference should be had to the following detailed description.

A particular aspect of the present invention is directed to theconversion of isobutylene to alpha nitratoisobutyric acid, alphahydroxyisobutyric acid and derivatives thereof. This is preferablyachieved by contacting isobutylene with dinitrogen tetroxide, andthereafter subjecting the resultant reaction products to further condi-In one preferred embodiment of the invention the further treatment ofthe nitrogen containing derivatives of isobutylene in the presence ofwater and an oxidizing agent selected from the group consisting ofoxides of nitrogen and nitric acid until a preponderance of suchintermediates are converted to the desired acid or acids. When theinitial reaction products or mixture are subjected to a furtheroxidation, then there can be recovered at least one product selectedfrom the group consisting of alpha nitratoisobutyric acid, alphahydroxyisobutyric acid and mixtures thereof. The resultant alphanitratoisobutyric acid can be readily hydrolyzed to the alphahydroxyisobutyric acid. When the resultant reaction products aresubjected to both a further oxidation and hydrolysis, then the productis predominantly alpha hydroxyisobutyric acid. The alphahydroxyisobutyric acid may subsequently be dehydrated or esterified orsubjected to both an esterification and a dehydration to producemethacrylic acid and suitable esters thereof. Alpha nitratoisobutyricacid can be converted to alpha alkoxy isobutyric acid compounds which inturn can also be converted to methacrylic acid and suitable estersthereof. 7

. The reaction between isobutylene and dinitrogen tetroxide preferablytakes place when there is present at lea-st one mole of dinitrogentetroxide per mole of isohutylene to be reacted. This initial reactionis prefertates atent ably carried out at relatively low temperatures andin particular at temperatures below about 40 C. The reaction productsresulting from the above initial reaction are then subjected to ormaintained under further conditions of oxidation and hydrolysis. In oneembodiment of the invention the secondary reactions are achieved bymeans of nitric acid at temperatures between about 0 and 150 C. forsuitable periods of time, which time period depends upon the particulartemperature employed. The concentration and quantity of nitric acidemployed for the secondary reactions can be varied considerably.

Specific detailed methods of practicing the present invention are setforth in the following non-limiting examples.

Example I 1100 grams of percent nitric acid and 215 grams of dinitrogentetroxide (2NO 2 N O were charged to a reaction vessel and cooled to atemperature of about 5 C., after which time isobutylene was slowlybubbled therethrough. 107 grams of isobutylene were added to thereaction mixture as it was stirred over a period of about 5 hours whilemaintaining the temperature below about 10 C. After all the isobutylenehad been fed, the reaction mixture was allowed to stand for about 16hours at ice temperature (0 C.). Vacuum distillation at about 25 C. overa period of about 20 hours was then employed to remove the nitric acidand nitrogen oxides.

The residue was treated with 1650 mls. of a 2 N aqueous solution ofsodium hydroxide at 60 C. for 24 hours. After acidification and etherextraction of the mixture, evaporation of the ether led to a solidresidue. The solid residue, recrystallized from a small volume ofbenzene, yielded a crop of crystals amounting to 114.8 grams. The yieldof alpha hydroxyisobutyric acid was thus 57.8 percent based on theoriginal quantity of isobutylene fed to the reactor.

Example II 1561 grams of a 70 percent nitric acid solution and 323 gramsof dinitrogen tetroxide (2NO 2N O were charged to a reaction vessel andcooled to a temperature of about 0 C., after which time isobutylene wasslowly bubbled therethrough. 109 grams of isobutylene were added to thereaction mixture as it was stirred over a period of about 5 hours whilemaintaining the temperature below about 5 C. After all the isobutylenehad been fed, the reaction mixture was allowed to stand for about 16hours at ice temperature (0 C.). The resulting mixture was distilled ina vacuum at about 25 C. over a period of about 20 hours to remove thenitric acid and nitrogen oxides. The residue was hydrolyzed in a mannersimilar to that illustrated in Example I. The yield of crystals obtainedin this run amounted to 139.0 grams. The yield of alphahydroxyisobutyric acid was 68.7 percent based on the original quantityof isobutylene fed to the reactor.

Example III A mixture of 100 parts of 70 percent aqueous nitric acid and20 parts of dinitrogen tetroxide was pumped into a stirred stainlesssteel reactor at a rate of about 9.2 grams per minute. Simultaneously astream of isobutylene was bubbled into the liquid in the reactor at arate of about 0.74 gram per minute. The liquid holdup in the reactor washeld constant by means of an overflow device. The average residence orreaction time of the reaction products in the reactor was on the orderof about 30 minutes. A coolant circulating through the jacket of thereactor served to hold the temperature constant at about 5 C. The flowswere continued until the composition of the eflluent solution remainedconstant 3 with respect to time and then long enough to allow a sampleto be collected.

The collected sample after being held at 15 C. for 2 hours was thensubjected to a vacuum distillation of dinitrogen tetroxide over a periodof 100 minutes. The reaction mixture was stirred and maintained at C.during this interval. Thereafter the mixture was poured into 180 gramsof 70 percent nitric acid. This solution to remove the oxides ofnitrogen. The residual solu- 5 was then held at 30 C. for 30 minutes.Yacuumdlstion was cooled to below about minus 20 C. and the tillationwas employed to remove the ,nltricacid and nitroalpha .nitratoisobutyricacid which precipitated out was g OXideS- The reamalmhg Tesldualselutloh a cooled recovered. This represented a ield of about 26.4 pert0ab0u t m1 2 n the alpha nltratolsobutyrle cent based on the quantity ofisobutylene fed to the ac1d 'Whleh Pfeelpltated u a fi d h A Yleld ofreactor. Infrared spectrum of the .mother liquor from 393 P e Of a pIlltratelsohutyne ac1d ha$ed on which the alpha nitrato acid wasprecipitated indicated the q t y of lsohutyleue e to the Ieaetlon thepresence therein of alpha hydroxyisobutyric acid and as Obtallledemother hq Was treated t a some alpha nitratoisobutyric acid. The nitricacid in 2 N aqueous solutwn of g u hydroxlde at 60 the mother liquor wasthen distilled off the residual :solufor about 18 hours. Afteracrdificauon and ether extraction hydrolyzed and worked up asillustrated in Exnon of the p t gn mlxture, gp t of the ample .I. Ayield of alpha hydro-xyisobutyr ic aeid'eorether l t a hd i T $01151resldue p eresponding to 38.8 percent based on the quantity of iisoa aYleld 0f alpha hydfeXylsehutyfle ac1d of about butylene fed to thereactor was obtained. Thus the total Percent based 011 the lseihutylehefed to h e yield of recovered material as .or convertible to alpha flThus, the tetal y f P as e011" hydroxyisgbutyric id was 652 percent, 20vertlble to alpha hydroxyisobutyric ac1d was 73.5 percent.

Example IV Example VI] 622 grams of 70 percent nitric acid solution and126 Dhutl'ogeh tetrOXide Was P p lute a surfed t grams of dinitrogentetroxide were charged to a reacless Steel reactor at rate of aboutgrams p tion vessel and cooled to a temperature of about minus me,slmultaueeusly a Stream Of lsebutylene Was added 15 C. after which timeisobutylene was slowly bubbled t0 the Ieaeter at a rate of aheut gramsPe therethrough. 56 grams of isobutylene were added to u about 3 melee Qdlhltl'egeh tetfelude P the reaction mixture as it was stirred over aperiod of {hole of tlsehutylehe Was being The hquld level about 5 hours.After all the isobutylene had been fed, the reactor was held eeustaht ymeans e an e the reaction mixture was warmed to C. and main- 30 how e Te average resldehee tune f e e tained'there for about 30 minutes. Theoxides of nitrotioh mlxture Wuhlh the Teaettu a about 30 mluutesgen werethen distilled off. The residual solution was A Coolant cueulatlhgthrough the Jacket efothe 'e cooled to a temperature below about minus20 C. and served to q g the temperature eotustaht at 5 iwhell the alphanitratoisobutyric acid which precipitated out o, the celhpesltleh 0f hfi e t Solu ion remained conwas recovered. This represented a yield ofabout 30.0 staut Wlth respect to tune, a Sample e t everfiOW Was percentb d on h quantity f isobutylene fed to the collected. 180 grams of 70percent nltrlc ac1d was added reactor. The nitric acid in the motherliquor was then mole of lsehutyleue fed during the 1l1teIVa1 '111distilled off and the residual solution hydrolyzed and Whlch the sampleg collected- The f'esultlflg sehltlefl treated as illustrated in ExampleI. A yield of alpha f h held at 30 for about 30 u Vacuumhydroxyisobutyric acid corresponding to 38.7 percent was 40 dlstluahohat a temperaturehelow then obtained. Thus, the total yield of recoveredmaterial ployed'to relhove y e g ultregen OXldeS- T as or convertible toalpha hydroxyisobutyric acid was remammg Fesldual soluhfm a cooled aboutminus 637 percent, .C. and the alpha nltratoisobutyric ac1d WhlCh pre-Example V clpitated out was filtered off. A yield of 23.2 percent ofalpha nitratoisobutyric acid based on the quantity "of Thls run a ti outmanner slmllar to that isobutylene fed to the reaction vessel during theperiod f Example IV f the exceptlon P (1) moles of in which the samplewas collected was obtained. An dlmtrogen tetroxlde per mole oflsobutYlefle were F amount of Water equal to the weight of nitric acidadded p f i 3 mole of Water were Substltuted for mmc earlier was addedto the mother liquor and the resulting ac1d, 2 the reaction temperaturewas f solution held at 60 C. for 24 hours. It was then evapthe holdmgtemperature and tune the macho? orated leavingaresidue containing mainlyalpha hydroxyture was lhour at 2t) C. The addition of Water instisobutyric acid with small amounts of alpha .uitratoof nitric ac1d todlnltrogen t6II:OX1d6 produc d a mixture isobutyric acid. The residuerepresented a yield of 42.5 contammg but a small fluanmy of mmc ac1d-There percent of alpha hydroxyisobutyric acid and alpha nitratel m thlsrun Percent of alpha isobutyric acid. Thus the total yield of product asor nitratolsobutyrlc acid and 28.3 percent of alpha hydroxytible t alphahydroxyisobutyric acid was 65.7 isobutyric acid. Thus the total ,yieldof recovered .matepercent rial as or convertible to alpha.hydroxyisobutyric acid Example VI was 67.4.percent. a

Example VI A series of runs were carried out in a manner similar to thatof Example VII. The dlfierences 1n cond1t1ons 55.6 grams of isobutylenewere passed into 360 grams and results of these runs are given in thefollowing table.

Run No 1 v 2 a 4 MoIesNzOmer Mole Isobutylene.- 2.18 3 4.l5 5L9.Moles%HNOsperMolesIsobutyl- 1.0 0 1.5 O. Hgl ging Period 30mins 30 mins.none 30 min's.

30 0 30 0 30C Yirelegclllpha Nitratoisobutyric Acid, 12.5 14.3 13.529.1. YieldAlphaHydroxyisobutyricAcid 52.5 40.6 58.4 38.7.

Percent. Total Yield, Percent 65.0 54.9 71.9.-- 67.8.

I About 2 moles of water per mole of isobutylene were added to themother liquor.

Example IX Dinitrogen tetroxide was pumped into a stirred stainlesssteel reactor at a rate of about 19.6 grams per minute. Simultaneously astream of isobutylene was added to the reactor at a rate of about 2.98grams per minute. Thus about 4.0 moles of dinitrogen tetroxide per moleof isobutylene were being fed. The liquid level in the reactor was heldconstant by means of an overflow device. The average residence time ofthe reaction mixture within the reactor was about 9 minutes. A coolantcirculating through the jacket of the reactor served to hold thetemperature constant at C. When the composition of the efiluent solutionremained constant with respect to time, a sample of the overflow wascollected over a period of about 17 minutes. The nitrogen oxides werethen removed at a temperature below C. and the remaining solution wasmaintained at 60 C. for 24 hours. vacuum leaving a residue of alphahydroxyisobutyric acid containing some alpha nitratoisobutyric acid. Thetotal yield of both these materials was 68.1%.

Example X A series of runs were carried out in a manner similar to thatof Example IX with the exception that various amounts of only water wereadded to the oxide-free solution. The results of these runs are given inthe following table.

It was then evaporated under room temperature under vacuum, leaving0.145 gram of white crystals, identified as alpha hydroxyisobutyric acidby its infrared spectrum.

Example XIV 118 grams of methyl alpha hydroxyisobutyrate (formed by theesterification of alpha hydroxyisobutyric acid with methanol) and a fewgrams of copper powder catalyst were charged to a reactor. 71 grams of P0 were added to the stirred reaction mixture over a period of about 15minutes. Upon completion of the addition, the reaction mixture was thendistilled and a yield of methyl methacrylate corresponding to 92.8percent was recovered.

The conversion of isobutylene to high yields of product as orconvertible to alpha hydroxyisobutyric acid is a multi-step or stagereaction which consists of an initial or first step wherein isobutylenereacts with liquid dinitrogen tetroxide at a relatively low temperatureto form a complex mixture of nitrogen-containing products.

The initial reaction proceeds very rapidly. For this reaction, there isemployed at least one mole of dinitrogen tetroxide per mole ofisobutylene employed. However, it has been found that there is someincrease in the yields with increasing amounts of dinitrogen tetroxide.Best results have been attained when more than one, and preferably fromabout 3 moles or greater, of dinitrogen tetroxide per mole ofisobutylene are employed. This initial reaction is exothermic andtemperature con- Run Number 5 6 7 8 Moles N204 per Mole Iso- 4.0- 4.05--4.05-- 6.15.

butylene. Reaction Temperature, O 0 n n 0, MolesHzO addedperMole 2.0.0.6-.- 1.0.-. 2.0.

Isobutylene. After Treatment C. for 1 hour; 60 C. for 24 100 0. for 400. for 1 hour; 60 0. for 60 0. for 23 hours. lhour. 1 hour; 100 0. for1.5 hours. hours. Yield Product, Per 75.2-. 68.7-- 65.7 82 7.

Example XI trol is very important. This reaction should be carried a I oA series of runs were carried, out 111 a manner similar out attemperaiures below about 40 f can be at to that of Example IX with theexception that various supeljatmosphenc reduced Pr'flssuresdesll'edamounts of both Water and nitric acid were added to With regardto the use of dinitrogen tetroxide, it should the oxide-free solution.The results of these runs are be noted that dinitrogen tetroxide is anequilibrium given in the following table.

ture of the monomer (N0 and the dimer (N 0 The Example XII A run wascarried out in a manner similar to that of Example IX except that theafter treatment given to the material collected from the reactor waslimited to distilling oil the nitrogen oxides under vacuum at atemperature below 5 C. The acidic portion of the residue was onlysuificient to account for a yield of 16 percent as alpha nitratoisobutyric acid. Infrared examination of the residue disclosed thepresence of alpha nitratoisobutyraldehyde, alpha nitratoisobutyricanhydride and alpha nitratoisobutyric acid. The infrared analysis failedto disclose the presence of any alpha hydroxyisobutyric acidJ ExampleXIII 0.242 gram of alpha nitratoisobutyraldehyde was treated with 0.142gram of 45% nitric acid for 18 hours at C. Thereafter the solution wasevaporated at 100 0. for 0.6 hour.

equilibrium concentration of the monomer is a function of temperature,as described in Inorganic Chemistry, F. Ephraim, 3rd English edition,New York, Nordman, 1939, page 667. When used in the specification andthe claims, the expression dinitrogen tetroxide is intended to includethe equilibrium concentration of the monomer there can be recovered invarying amounts alpha nitratoisobutyric acid, and alphahydroxyisobutyric acid. When the initial reaction products are subjectedto both further conditions of oxidation and hydrolysis, then the productrecoverable is predominantly alpha hydroxyisobutyric acid.

The treatment of the nitrogen-containing reaction intermediates can becarried out in several ways. For example, the further oxidation of theinitial reaction products can be accomplished by maintaining thereaction products at a temperature between about and 150 C. In thisembodiment it is believed that the oxidation of the aldehyde isaccomplished by an intramolecular oxidation. That is, there is efiecteda decomposition or degradation of some intermediate nitrogen-containingcompounds to yield nitrogen oxides and appreciable amounts of waterwhich bring about oxidation of the alpha nitratoisobutyraldehyde andsome hydrolysis of the alpha nitrate.- isobutyric anhydride and/orresultant alpha nitratoisobutyric acid to alpha hydroxyisobutyric acid.Thus, the only treatment required to convert the initial reactionproducts to alpha hydroxyisobutyric acid and alpha nitratoisobutyricacid is an additional standing at a temperature between about 0 C. and150 C., preferably above about C., for a suitable period of time whichcan be but minutes. No addition of water and/ or nitric acid isrequired.

However water and/or nitric acid can be added to facilitate a morecomplete oxidation and hydrolysis so that the product recoverable ispredominantly alpha hydroxyisobutyric acid. When it is desirable to addadditional water to effect relatively complete hydrolysis of thehydrolyzable products, it can be done at any point in the process.Likewise, when it is desirable to add additional nitric acid for anyreason, e. g., as an oxidant or to catalyze the hydrolysis reactions, itcan also be done l at any point in the process as is illustrated in theexamples. Additional hydrolysis of the alpha nitratoisobutyric acid ofthe alpha hydroxyisobutyric acid can be accomplished .by the use ofwater, aqueous acid solutions, or

aqueous alkali metal hydroxide solutions. Additionally the hydrolysiscan be carried out as a separate and distinct step from the oxidation ofthe reaction products or it can be merged with the oxidation so as toinvolve but one step. The alpha nitratoisobutyric acid or alphanitratoisobutyric anhydride produced can be recoveredand subsequentlyhydrolyzed or they can be hydrolyzed while contained in the reactionmixture.

Similarly the intermediate alpha nitratoisobutyraldehyde may be isolatedand further oxidized to the desired acid by use of ordinary oxidizingagents such as oxygen, hydrogen peroxide, potassium permanganate,nitrogen oxides, nitric acid and the like.

Alpha nitratoisobutyn'c acid can be selectively recovered from thereaction mixture by cooling or chilling the resulting reaction mixtureto a low temperature so as to achieve a precipitation or crystallizationof the alpha nitratoisobutyric acid. In one preferred embodiment, thereaction mixture is chilled or cooled to temperatures below about 0 C.The desired alpha nitratoand alpha hydroxyisobutyric acids can beseparated from the reaction mixture and from each other as such or theycan first be converted to esters, amides, insoluble metal salts or otherderivatives and then separated. The preparation of the esters,amides,-salts and the like of these acids can be accomplished byw'elbknown techniques such as is illustrated in U. S. Patents 1,775,636;1,927,295 2,245,483; 2,336,317; 2,348,710; 2,355,330; 2,362,326;2,383,897; 2,811,546 and Journal Organic Chemistry 3, 312 (1938).

The-term acid as used in the specification and claims is thus intendedto include esters, amides, anhydride, salts and other'functionalderivatives obtained by modification of the carboxyl group and/ or alphasubstituent.

The feed material need not comprise pure isobutylene. It is possible touse a mixture of isobutane and isobutylene as it has been found thatisobutane does not react appreciably under these conditions. f

The alpha hydroxyisobutyric acid obtained may be esterified ordehydrated or subjected to both an esterification and a dehydration. Ifesters of the alpha hydroxyisobutyric acid are desired, then the alphahydroxy- Likewise, if an ester of methacrylic acid is desired, then thealpha hydroxyisobutyric acid may be esterified with a suitable alcoholand the ester dehydrated. The dehydration may be accomplished by meansof P 0 or by any of the procedures shown in British Patent 409,733 or inU. S. Patents 1,993,089; 2,054,242; 2,100,993; 2,184,934; 2,226,645;2,244,389 and 2,356,247.

Alpha nitratoisobutyric acid can be converted to methacrylic acid andesters thereof by the procedures described in U. S. Patent 2,816,921,British Patent 584,607 and Journal American Chemical Society 7 0- 53 (1.8)

Since certain changes may be made in the above process without departingfrom the scope of the invention herein involved, it is intended that allmatter contained in the above description shall be interpreted asillustrative not in a limiting sense.

What is claimed is:

1."In the process of producing acids selected from the group consistingof alpha nitratoisobutyric acid, alpha hydroxyisobutyric acid andmixtures thereof wherein isobutylene is reacted with liquid dinitrogentetroxide to form some of the desired acids and othernitrogen-containing derivatives of isobutylene which are intermediatesin the conversion of isobutylene to the desired acids, the improvementwhich comprises maintaining said intermediates in the presence of waterand an oxidizing agentselectedfrom the group consisting of oxides ofnitrogen nitric :acid until a preponderance of such intermediates areconverted to the desired acids, and separating one of said acids fromthe reaction medium and from the other of said acids.

2..The .process of claim 1 wherein the water is-ob tained as a.byproduct in the formation of the intermediates.

3. The process of claim 1 wherein the intermediates are held inthepresence of the water and the oxidizing agent at a temperature above 15C. and below C. for a time in excess of 30 minutes.

4. The process of claim 1 wherein the intermediates are-held at atemperature above 60 C. in the presence of thewater and the oxidizingagent.

5. The process of claim 1 wherein at least 1 moleof water is added foreach mole of isobutylene in the reaction intermediates and theintermediates are maintained inthe presence of the added water and theoxidizing agent until said intermediates are converted to alphahydroxyisobutyric acid.

6. The process of claim 1 wherein nitric acid and water are added to theintermediates, there being at least 1 mole of water and at least 1 moleof nitric ,acid for each mole of isobutylene in the reactionintermediates and the intermediates are maintained in the presence ofthe added nitric acid and water until a preponderance of suchintermediates are converted to alpha hydroxyisobutyric acid.

7. The process of claim 1 wherein a substantial amount of nitric acid ispresent along with the liquid dinitrogen tetroxide during the initialreaction between the dinitrogen tetroxide and isobutylene.

8. The process of claim 1 wherein dinitrogen tetroxide is removed fromthe reaction mixture and water is then added to the residual reactionmixture.

9. The process of claim 1 wherein the nitric acid is obtained as abyproduct in the formation of the intermediates.

10. In the process of producing an acid selected from the groupconsisting of alpha nitratoisobutyric acid, alpha hydroxyisobutyric acidand mixtures thereof wherein isobutylene is reacted with liquiddinitrogen tetroxide to form some of the desired acids and substantialquantities of alpha nitratoisobutyraldehyde, the improvement whichcomprises oxidizing the alpha nitratoisobutyraldehyde to the desiredacid.

No references cited.

1. IN THE PROCESS OF PRODUCING ACIDS SELECTED FROM THE GROUP CONSISTINGOF ALPHA NITRATOISOBUTYRIC ACID, ALPHA HYDROXYISOBUTYRIC ACID ANDMIXTURES THEREOF WHEREIN ISOBUTYLENE IS REACTED WITH LIQUID DINITROGENTETROXIDE TO FORM SOME OF THE DESIRED ACIDS AND OTHERNITROGEN-CONTAINING DERIVATIVES OF ISOBUTYLENE WHICH ARE INTERMEDIATESIN THE CONVERSION OF ISOBUTYLENE TO THE DESIRED ACIDS, THE IMPROVEMENTWHICH COMPRISES MAINTAINING SAID INTERMEDIATES IN THE PRESENCE OF WATERAND AN OXIDIZING AGENT SELECTED FROM THE GROUP CONSISTING OF OXIDES OFNITROGEN AND NITRIC ACID UNTIL A PREPONDERANCE OF SUCH INTERMEDIATES ARECONVERTED TO THE DESIRED ACIDS, AND SEPARATING ONE OF SAID ACIDS FROMTHE REACTION MEDIUM AND FROM THE OTHER OF SAID ACIDS.